The development of polyolefin resin with high performance was dependent on continual enhancement of behavior of the olefin polymerization catalysts. In U.S. Pat. No. 4,298,718 and U.S. Pat. No. 4,495,338, proposed firstly was the activated magnesium halide as a carrier supporting the Ziegler-Natta catalyst, wherein the catalysts produced from the carrier and titanium tetrachloride exhibited high activity in propylene polymerization, but was poor in stereospecificity. Subsequently, the constant effort was made by research staff to improve the catalyst behavior. In GB2,111,066, disclosed was polypropylene having high isotacticity prepared by contacting magnesium chloride alcoholate with liquid titanium compound while adding an electronic donor (such as phthalate) to give a solid titanium catalyst, and then adding another electronic donor (alkoxysilane compound) for olefin polymerization. The solid catalyst component disclosed in EP0361,494 comprised activated magnesium halide, a titanium compound supported thereon and having at least one Ti-halide, and organic diether or polyether, such as the catalyst prepared with 1,3-diether as the electronic donor compound. Without addition of the external electron donor, the catalyst system was used for polymerization to provide polypropylene having high isotacticity, and was highly active. In CN1,143,651A, further improvement was made on the internal and/or external electron donor in the type of catalysts, wherein 1,3-diether used in the system had a carbon atom at 2-position bonded with an organic group having two or three unsaturated bonds to provide a monocyclic or polycyclic ring structure, i.e. polyene-1,3-diether ring, allowing the activity and stereospecificity of the catalyst to improve to a certain extent. CN1,306,544 described that succinate was used as the internal electron donor, and the prepared catalyst exhibited high activity and stereospecificity when used for catalyzing propylene polymerization, and provided polypropylene with broad molecular weight distribution.
From the typical catalytic polymerization system above, the electron donor had an influence, to a greater or less extent, on the activity and stereospecificity of the catalyst and polymer perfomance, and played a critical role in the tacticity of polypropylene. Therefore, development of polyolefin catalyst was optimization of available electron donor and development of novel electron donor. Most of the electron donors currently reported was the phosphorus, nitrogen, oxygen-containing compound, such as carboxylate, ether, organophosphorus, amine, silane compounds, and was classified into monoesters, diesters (including succinate, alcohol esters), and diethers. It was found during research that the estersil compounds used as the internal electron donor had a special reactivity with titanium compound and magnesium compound, and thus prepared catalysts exhibited very high activity and stereospecificity when used for catalyzing olefin polymerization.